The use of spray booths does not reduce NMVOC-emissions. Above all, spray booths havebeen introduced in order to assure good working conditions. Moreover, these spray boothshave proved to lower the drying time and to improve the quality of coating.Figure shows a spray booth, which can be considered as representative for the wholesector of vehicle refinish coating, including the ‘combi’ type [2]. The air has a temperature of20 to 25 °C for the coating step, and is heated to 60 °C for the drying step [17]. The meansolvent concentration in the waste gas is in the range of 50 – 75 mg NMVOC/Nm3 [5, 6].1.2

Application Technique

It is assumed that the majority of the coating activities in vehicle refinishing (ca. 95 %) iscarried out by pneumatic spraying [7, 8] with an application efficiency estimated atapproximately 30 % [25]. Paint application with HVLP guns (High Volume, Low Pressure)leads to an increase of the application efficiency by 10 – 20 % compared to conventionalspraying guns [27].Airless and air assisted airless spraying are not adapted to the vehicle refinishing sector, due tothe high consumption of coating, the necessity of special equipment, and the rather poorquality achieved for the coating of small surfaces. Therefore, these technologies are appliedonly in the truck repair sector and for the coating of large surfaces. [9]Electrostatic application is not practicable in the car refinishing sector, because its use canresult in damages to the electronic and plastic parts of vehicles [9].Other non-spraying techniques like dipping or brushing are as well not applicable for vehiclerefinishing [9].1.3

Coating Structure

The painting of a car consists of 3 or 4 layers1 [2]:•the first coat (primer) protects the car body against corrosion;•the second coat (surfacer) compensates unevenness of the car body in order to have asmooth under-coat and to have the next coats fixed. In some special cases, only one coat isused which simultaneously serves as primer and surfacer;•the third coat (basecoat or topcoat) is either an effect-coat or a uni-coat, giving the carbody its colour;•the fourth and last coat (clearcoat) improves the resistance against weathering, sun, stoneprojections, scratches. This coat is not always necessary when a uni-coat is used, becauseuni-coats can combine the functions of basecoat and clearcoat